FIG. 8 shows a rotary support device which is conventionally used and in which balls 4 are arranged in a row between the peripheral wall 13 of an under ring 1 and the peripheral wall 23 of an upper ring 3.
When an article (not shown) is placed on a pallet 8 as placed on the device, the article can be lightly rotated along with the pallet, hence convenience.
However, the conventional rotary support device has the problem that it is low in durability against thrust loads despite its high durability against radial loads. This problem is attributable to the following construction. As will be apparent from FIG. 8, the peripheral walls 13, 23 of the under ring 1 and the upper ring 2 are approximately perpendicular to the plane of rotation of the support device, so that the area of contact of the balls 4 in guide grooves 15, 25 formed in the opposed surfaces of the walls 13, 23 with the grooved portions 15, 25 is much smaller in the thrust direction than in the radial direction.
Furthermore, the support device is assembled by fitting the upper ring 2 to the under ring 1, then placing the balls 4 into the space between the ring walls 13, 23 through a hole 14 formed in the inner ring, and thereafter closing the hole 14.
Further, the support device failed to provide between the rings with any retainer for holding balls.